Date: Tue, 25 May 1999 08:03:08 -0700 From: Cy Schubert <cschuber@uumail.gov.bc.ca> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Cy Schubert - ITSD Open Systems Group <Cy.Schubert@uumail.gov.bc.ca>, dg@root.com, Cliff Skolnick <cliff@steam.com>, Mike Tancsa <mike@sentex.net>, freebsd-stable@FreeBSD.ORG, luoqi@FreeBSD.ORG Subject: Re: vm_fault deadlock and PR 8416 ... NOT fixed! Message-ID: <199905251503.IAA33951@passer.osg.gov.bc.ca> In-Reply-To: Your message of "Fri, 21 May 1999 20:04:47 PDT." <199905220304.UAA69597@apollo.backplane.com>
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In message <199905220304.UAA69597@apollo.backplane.com>, Matthew
Dillon writes:
> :Would plan B risk corruption of any data? Could itself be the likely
> :cause of any potential panics?
> :
> :Assuming plan B has no major risks, this might be a temporary
> :workaround until we can wrap our minds around this one. It's just a
> :rework of Luoqi's patch, just in case we want to try plan B again.
> :
> :--- kern_lock.c.orig Tue May 11 08:34:52 1999
> :+++ kern_lock.c Wed May 12 05:38:52 1999
> :@@ -215,7 +215,9 @@
> : * lock itself ).
> : */
> : if (lkp->lk_lockholder != pid) {
> :- if (p->p_flag & P_DEADLKTREAT) {
> :+ if ((p->p_flag & P_DEADLKTREAT) ||
> :+ ((lkp->lk_flags & LK_SHARE_NONZERO) != 0 &&
> :+ (flags & LK_CANRECURSE) != 0) {
> : error = acquire(
> : lkp,
> : extflags,
> :
> :If this workaround doesn't work, then setting error = 0 and allowing
> :the code to fall through to the subsequent sharelock may be our only
> :choice for now.
> :
> :The other point I wish to make for all on this list is that Matt's
> :patch fixes a read()/mmap() deadlock. It doesn't fix a write()/mmap()
> :deadlock.
> :
> :
> :Regards, Phone: (250)387-8437
> :Cy Schubert Fax: (250)387-5766
>
> It's an interesting workaround, but a bit too complex. That is, the
> locking is becoming a too complex. We are going to screw ourselves if
> we keep patching it. ...
I came to the same conclusion last week.
Regards, Phone: (250)387-8437
Cy Schubert Fax: (250)387-5766
Open Systems Group Internet: Cy.Schubert@uumail.gov.bc.ca
ITSD Cy.Schubert@gems8.gov.bc.ca
Province of BC
"e**(i*pi)+1=0"
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